Overflow drains are secondary drains that work in tandem with primary drains to prevent an overflow or spillage of liquid out of some type of receptacle. Their main function is to ensure that damage is not caused to the area surrounding the receptacle as a result of the liquid reaching the rim of the container and flowing into the area unchecked. These drains are often located an equitable distance from the lip or rim, but still significantly higher than the primary drain located at the bottom of the receptacle.
A classic example of an overflow drain is found in many homes. Most bathroom tubs and sinks are equipped with this secondary drain as a means of preventing water from spilling onto the surrounding floor and causing water damage. With the tub, the overflow drain is often located several inches below the tub rim and helps to minimize the chances of the tub overflowing while a bath is being drawn.
In like manner, an overflow drain is also found in the bathroom sink. As with the bathtub, the presence of this secondary drain in the sink helps to prevent the basin from filling completely and possibly overflowing onto the surrounding floor. This simple design element can mean that the chances of water damage to the flooring and possibly baseboards in the room are significantly lower.
An overflow drain is also used in manufacturing plants and other commercial assembly operations. The drain may be used to redirect water after it reaches a certain level, or serve as a means of effectively maintaining a certain level of any type of liquid in place as part of the manufacturing process. In both domestic and commercial applications, the overflow drain is coupled with overflow plumbing or tubing that makes it possible to route the excess liquid safely away from the receptacle.
As with any type of drain, there is always the possibility of an overflow drain becoming clogged. When this occurs, it is usually a good idea to call in a plumber. A plumbing professional will be able to accurately evaluate the type of plumbing or tubing used in the construction of the drain and remove the blockage using methods that will not damage the secondary draining channel.